Earthlings have long considered the possibility of colonizing Mars, but so far this planet is completely unsuitable for life, at least due to the low temperature. Now American physicists have proposed a way to warm the Red Planet with the help of metal nanoparticles sprayed on its surface. This method could seal the atmosphere and melt subsurface ice.

Traces of large rivers, streams, and reservoirs have been discovered on the surface of Mars long ago, indicating that the Red Planet was habitable. It is now a desert with ice caps at the poles and liquid water below the surface. Mars was left without water by an event that stripped it of its dense atmosphere; today, it is a thin layer of carbon dioxide that is 61 times less dense than Earth’s atmosphere.

The greenhouse effect is therefore too weak to maintain a suitable temperature: the current atmosphere adds only five kelvins to the temperature. And these conditions would not allow life to arise or at least to survive if brought from Earth.

Some temperature fluctuations occur during dust storms; one such effect was recorded in 2018, when a “dust blanket” covering the Red Planet heated the air near the surface by almost one kelvin.

To return Mars to its former temperature, a group of American physicists proposed to sprinkle artificial dust made of nanorods of aluminum and iron on its surface. Blown tens of kilometers away by the wind, Martian dust scatters and absorbs thermal radiation. A similar aerosol effect can be achieved using nanoparticles the size of ordinary sparkles. The results of the scientific work are published in the journal. Science Developments .

Using a climate model with a multilayered atmosphere, physicists simulated the effect of nanorods nine micrometers long and 0.16 x 0.16 micrometers in cross-section (60:1 aspect ratio). Calculations showed that this type of metal dust, which obeys Brownian motion, absorbs and scatters sunlight more actively than Martian dust and will settle over about 10 years. The greenhouse effect that would occur after the nanoparticles were sprayed during the hottest part of the year would create conditions almost five thousand times more effective than current conditions in melting groundwater.

The first emission, as scientists say, could be carried out using a pipe up to 100 meters high and at a speed of 30 liters per second (for comparison, a typical garden sprinkler sprays one liter of water per second). The lifetime of the particles could be increased if the design allowed the particles to rise on their own, instead of waiting for the strong Martian wind. The model showed that such an aerosol could raise the planet’s global temperature to 245 Kelvin, or minus 28.15 °C. The current average temperature is 210 Kelvin, or minus 63 °C.

According to physicists, after a few months of warming, the atmospheric pressure on the Red Planet will increase by about 20%, and then by another 2-20 times. It may take centuries for the atmosphere to compress; that’s how long it takes for carbon dioxide to evaporate. However, researchers emphasized that such warming will not make Mars suitable for life with oxygenic photosynthesis. There is not enough oxygen in the Martian air for cyanobacteria, and there is too much perchlorate in the soil.

The proposed method has several disadvantages. First, the particles will need to be coated with a thin hydrophobic material to prevent them from icing up.

Second, creating such a large number of nanorods would require one percent of the world’s metal production. And they still need to be processed. Although the metal could be replaced with biosynthesized magnetite or carbon nanomaterials with a width of less than two nanometers. The authors of the study concluded that graphene could cope more effectively with the warming of Mars.